laying the cards on the table!

Ok!
So here I go again. I have tried to figure this out for too long now and asked too many questions here on the forum.
therefore I will try to sum up my problems in one post for you experts to ponder.


Problem and symptoms
Engine dies on idle
When properly warm engine would rev up (around 4000) and sit there.
Engine returned to idle very slowly.
These problems all still exist but manifest themselves a little differently.

The bike now performs quite well when cold. Holds a steady idle around 1050 until it gets warm. When revved it still returns to idle very slowly.
What has been done so far?

Valve Clearance checked with metric feel gauge with .05 increments. Pic indicate which gauge that fit. Have not had the time to replace any shims nor do I have the tool (yet).

Cleaned carbs.

Replaced idle mix o-ring, throttle shaft seals, fuel line o-rings and swapped bolts holding the butterfly valve plates.

Clunk tested carbs.

Bench synced carbs according to: http://xj650.blogspot.com/2009/04/how-t ... carbs.html

Lubed throttle and ”choke” cables; they both run smoothly.

Problems with service
Can not get fuel drain screws out so I can not perform a float level test with clear tube.
With the carbs dry and up side down I tried to blow air in to the fuel line and all needle valves are tight. There is also no fuel leakage when carbs are mounted on bike.

Can not seem to get the enrichment circuit wells properly cleaned as specified in http://xj650.blogspot.com/2009/01/how-t ... -well.html
Using the fuel enrichment aka Choke works well. Engine fires up even when cold.

Set idle mix screws to 2.5 out.

Events/tests
Even though I had spark #3 would not fire earlier today. Now that I have been riding it a little more it seems to fire on all cylinders.
Have tried cutting out one cylinder at the time. Characteristics change but problem with high and hanging idle persists.
Searched for vacuum leaks with starter gas and propane torch. None found.

 

Check idle adjustment - this can screw itself in and out with vibration. This adjustment is VERY, VERY sensitive. Otherwise it sounds like a lean mixture.

 

If those measurements are metric, all of your exhaust valves are HORRIBLY tight; and you have ONE intake valve in spec.

Why in the world are you trying to adjust the carbs when you're about to cook exhaust valves 2, 3 and 4???

I'm sure the bike runs FINE until it warms up; then the valve clearances tighten up even further when it gets hot.

GET THE BLOODY VALVE CLEARANCES IN SPEC; right now you're flying down "Valve Job Lane" with no brakes and there's a lady pushing a baby carriage across the street.

Everything else is a waste of time with those valve clearances, honest. Quit screwing with the carbs; it's no wonder you're getting nowhere.

There are alternatives to "the tool:" http://xjbikes.com/Forums/viewtopic/t=29209.html

Get on the valves.

 

Sounds like what I had happen. It would start off decent idle then shoot up high. What it was for me was the bike would warm up and go to an idle that was set too high. Turned down the idle screw till it was where I wanted it. But first I agree with Fitz get those valves in spec.

 

Fuel drain screws removal

http://www.xjbikes.com/Forums/viewtopic/t=4281.html

 

i got a seized float bowl drain screw out with a handheld impact wrench. might be worth a shot.

 

Bench Syncing with Paper Clips STARTS you off with the Throttles Open.
Not good.
You want the Throttles ==> CLOSED.

Use 3X5 Card, Business Card, Resume Paper or strips cut from a Dannon Lite & Fit Yogurt Package.

If you can't "Sight Tube" all four Floats. Measure and Set at least one.
Then, measure the Height of the Float on your one "Good one" and set the other three at the same height.

A Toothpick glued to the Pocket Clip of a Precision Ruler will do the trick!

 

Allright.

I am getting the valves done asap.
Checked them today - only problem is that my feeler gauge goes from 0.05 to 0.10, 0.15, 0.20 etc This means I cant get a super reading.

From checking my intake valves (pic above) I reckon they are fine.

My exhaust though are (from left to right)
Thickest possible feeler gauge: 0.15 0.10 0.10 0.10
Shim installed: 260 270 260 255

Will replace with: none 265 255 250

Does anyone oppose these changes?

 

I would grab a set of feelers from your local auto parts store that is made for tappets. precision is key here as if your wrong your engine will pay the price. Also you may find once you swap the shim you may need to go smaller still. I know some of us here were talking about making a shim pool on the pay it forward thread. You may be able to get the shims you need from some of the folks on this site. Also add to profile signature the make and model of your bike as well as location so people will be able to help you easier.

 

Your intake valves (except #2) are at 0.10mm; spec is .11mm~.15mm; so three of the four are tight. They're NOT fine.

ALL of your exhausts are way tight.

Going "down" one shim size on an exhaust valve measuring .10mm will only take it to .15mm, still too tight. On the EXHAUST valves measuring .10mm, you'll need to go two sizes down.

You have ONE VALVE IN SPEC; intake #2. ALL of the rest of them are too tight.

I highly recommend the K-D Tools pn 2274 metric feeler: http://www.google.com/products/catalog? ... C4Q8wIwAg# It will make the task much easier.

 

UGH... i just typed up a long response, and it didn't post!

Listen to Fitz, get them valves taken care of first. There's a sticky on the stuck drain screws - gotta get them taken care of. 2 of my carb drains were filled in w/ some kind of epoxy to fix the partially removed drain screws that stripped (that was a b**ch). Len (chacal) has some drain screws with allen heads - go for them - much easier. "Close enough" doesn't cut it with these carbs" Trust me... I did it 8 times at "close enough". Ended up calling Rick, for him to tell me the same thing. "Close enough" doesn't cut it. Did it the right way the 9th time... what do you know? it worked.

Also, we're missing some info: bike? pods vs airbox? stock exhaust? other mods? Also, are you using a haynes manual? (2 jets are reversed)

 

Glad I am getting so much help from everyone.

Fitz. It says in the pic 0.10 but (like I wrote) the clearance is between 0.10 and 0.15 which is the next gauge up. I am certain my intakes are all within spec.

I manged to get a hold of a guy who happens to be a motorcycle enthusiast and he has a whole bunch of shims so my airhead valves are all within spec now!

I quickly got the bike ready and ran it for a little while. Just like before it idled fine, perhaps a little better now.
I revved it and it slowly came back down again.
Then, when it became hot, it crept up and stayed up.

So my problem is the same, more or less, eventhough my valves are in spec.
It appears quite natural to me though, the revving engine must depend on fuel/air getting in and not so much the valve clearance. I understand that correct clearance is crucial for being able to tune the engine with carbs.
I am new to engines so perhaps I am missing some fundamentals here but thats how I understand the problem of my revving engine.

Well, like I wrote above I am really glad that you all take interest in my machine and want to help me solve the problem.
Next thing I will remove the carbs (yet again and reposition the butterfly valves to see if I can get them to close even further. It might be just some kind of stupid mistake on my behalf like forgetting to install throttle shaft seals or doing it incorrectly.

 

OK, but now that your valves are in spec, you should be able to ACTUALLY SYNC the carbs; something that wouldn't have worked before.

If they're as clean as you say, AND the floats are set correctly AND they've been bench-sync'ed; then just do a running vac sync (YICS blocked if applicable) and your problem should be solved unless you have a vacuum leak somewhere.

 

When it rolls to that high rpm turn down the idle. That was my problem I just never knew it LOL

 

Allright! New progress!

Took the rack off and bench synced again. I am getting better at this now an managed to get all fully closed (so only the idle mix hole is visible).

With this promising progress i quickly reattached the rack and started playing around with the mix screws. Got the bike to idle around 1050-1150 when hot!
I pressed down on the sync screws and that made the idle fall more rapidly. A strange thing is that I can feel a distinct tap of plinking (without the sound) when i press upon the sync screw between 3 & 4 (the one furthest to the right). However I could not see any movement of the throttle axle so I figure that the vacuum isnt sucking air past the butterfly valve. Could be that I am wrong though, perhaps the throttle shaft springs are too weak?

When I blipped the throttle, it sort of lingered and slowly went back down again.
I took it for a ride! Goes well but idles high, not at all like before but still.

Just to make sure that there are still no vacuum leaks I sprayed starter gas to certain areas and I was very surprised that the idle speed went down when I sprayed on the underside of the carb/head manifolds/camchain tensioner! I repeated it a few times and it seemed to behave the same way if ever so slightly.



I am leaving on a spearfishing trip tomorrow, which will be followed by the military world games in Rio de Janiero. This means that my bikeproject unfortunently has to wait a few weeks before I can get to doing the things Fitz recommended.

 

Sounds like you forgot to sync the carbs. Also you should pull the mix screw out 2 1/2 rurns as a starting place then after a vac sync you have to colourtune them. That spraying on the head manifold thing sounds odd. Good luck.

 

Yeah, you are right. I havent gotten around to do a vac sync yet. Will try to do that in the end of july.

Thanks for your help. I will post again when I have made progress

 

You keep saying that you "Quickly" did this, and "Quickly" did that. Please don't do anything quicky, take your time with things.

You do things quickly, and that's when mistakes can happen, where you could miss things or forget things.

Rule of thumb, do things slowly and methodically, do it right.

 

the 4000rpm hold kept happening to me, only way to keep it between 1000 and 35000 is with a combination of choke and throttle, and if it got to 4k, it would get stuck and I'd have to hit the kill switch and turn it back on when it dropped to 2k, turned out one of the stoppers fell off on the carb manifold leaving a hole / air leak in one cylinder. Check for air leaks. Good luck